Probably not to be honest. As far as I am aware the M4 feed ramps were introduced as part of a reliability package to address issues of firing full auto with the fast cyclic rate/high bolt velocity of the short carbine gas system combined with the longer/pointier bullet in the M855 round.

I have heard of some issues when mixing and matching M4 barrel extensions with standard A3 uppers due to a slight ridge that can be problematic on the transition from the upper to the barrel extension but I have no experience and that may all be hearsay.

the M4 got its name from the m-4 feed ramp. thats why the m4 is the m4, not the m16a6 or m177a4 or some such -- it got a new name so it could be sold to the DOD as a new weapon system.

it was a insider deal to get more money from uncle sugar as best as i can tell.

the m4s bullet guides ramps are cut deeper and longer than an a1-a2-- supposedly for heavy long bullets.

i can't see that they help much because the bullets got to be nose diving really bad to even get on that part of the ramp-- good mags fix the problem. and a run a lot of long heavy bullets in 20"s without the m4 ramps.

the m4 ramp might be helpful on a 6.8,6.5,7.62x39 or 300BO because the bullet is bigger and may get a little more contact with the ramps.

the m4 ramps don't hurt anything --but it is very hard to tell IF they help at all-- but colt got a LOT more $$$ out of um.

it is OK to run a m4 barrel in a a2/a3 upper , running a a2/a3 ramped barrel in a m4 upper can cause an issue cause it leaves a bump in the ramp.

generally i don't concern myself with the m4/a2 ramps less it is the m4 upper with the a2/a3 ramped barrel. other wise it is mix and match time.